Electric motor turbine-type fuel pumps have been used in, for example, automotive fuel delivery systems. Pumps of this type typically include a housing adapted to be immersed in a fuel supply tank with an inlet for drawing fuel from the surrounding tank and an outlet for feeding fuel under pressure to the engine. A turbine impeller is coupled to a rotor driven to rotate by the electric motor and has an arcuate pumping channel surrounding its periphery for developing fuel pressure through rotation of the impeller. One example of a fuel pump of this type is illustrated in U.S. Pat. No. 5,257,916.
In fuel pumps of this type, the impeller is received between a pair of bodies disposed on each side of the impeller and in use, fuel leaks through the clearances between the impeller and the bodies. To reduce this leakage loss, the clearances between the impeller and the adjacent bodies are designed to be extremely small. Thus, especially if the dimensional accuracy of the impeller and the adjacent bodies is low, an unbalanced pressure acting on the impeller will generate an increased frictional resistance to rotation of the impeller between the bodies and as a result, increases the wear of the impeller in use and the operating torque required to rotate it thereby decreasing the efficiency and life of the pump.
One attempt to solve this problem is disclosed in U.S. Pat. No. 4,854,830 which provides for so-called pressure compensation hollows and/or grooves formed in the impeller. The hollows and/or grooves are constructed to communicate with fuel adjacent opposed faces of the impeller to balance the impeller between opposed surfaces in the fuel pump.